/**
 * ***************************************************************************** Copyright (c) 2000,
 * 2008 IBM Corporation and others. All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0 which accompanies this
 * distribution, and is available at http://www.eclipse.org/legal/epl-v10.html
 *
 * <p>Contributors: IBM Corporation - initial API and implementation
 * *****************************************************************************
 */
package org.eclipse.ltk.core.refactoring;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.ltk.internal.core.refactoring.RefactoringCoreMessages;

/**
 * A refactoring change that does nothing. The reverse change of a <code>NullChange</code> is a
 * <code>NullChange</code>.
 *
 * <p>Note: this class is not intended to be extended by clients.
 *
 * @since 3.0
 * @noextend This class is not intended to be subclassed by clients.
 */
public class NullChange extends Change {

  private String fName;

  /** Creates a new <code>NullChange</code> with a default name. */
  public NullChange() {
    this(RefactoringCoreMessages.NullChange_name);
  }

  /**
   * Creates a new <code>NullChange</code> with the given name.
   *
   * @param name the human readable name of this change
   */
  public NullChange(String name) {
    Assert.isNotNull(name);
    fName = name;
  }

  /** {@inheritDoc} */
  public String getName() {
    return fName;
  }

  /** {@inheritDoc} */
  public void initializeValidationData(IProgressMonitor pm) {
    // do nothing
  }

  /** {@inheritDoc} */
  public RefactoringStatus isValid(IProgressMonitor pm) throws CoreException {
    return new RefactoringStatus();
  }

  /** {@inheritDoc} */
  public Change perform(IProgressMonitor pm) throws CoreException {
    return new NullChange();
  }

  /** {@inheritDoc} */
  public Object getModifiedElement() {
    return null;
  }
}
